(1) Field of the Invention:
This invention relates to an apparatus for sealing the skirt of recovery systems which collects the valuable waste gas from an oxygen blowing converter.
(2) Description of the Prior Art:
Oxygen blowing converters generate large quantities of waste gases rich in CO content during the refining of metals by pure oxygen blowing. It is well known to collect such waste gases in the unburnt state at the exit from an oxygen blowing converter to use the CO gas contained in them for various valuable purposes. This is normally done by a waste gas recovery apparatus.
A typical recovery apparatus is illustrated schematically in FIG. 3, which is connected to a converter 1 for steel production to draw the waste gases therefrom. A lance 10 is provided for blowing pure oxygen onto the bath of molten pig iron within the converter 1. As is well known, the operation of a converter comprises the three process steps of charging, blowing, and discharging. In the blowing step, pure oxygen is blown through an oxygen lance or jet into molten metal in the converter to accomplish refining. The oxygen thus blown and carbon within the molten metal react to form a large quantity of waste gas composed principally of CO. The recovery apparatus includes a fan 6 which is rotated to create a draught that draws by suction the waste gases from the converter into a gas cooler 3.
A dust collectors 4 and 5 are provided to remove the dust contained in the gases before they are conducted into a gas holder 7.
A divergent duct branches off from the main duct at a junction point and is connected at its opposite end to a stack 8. A damper 9 is provided immediately downstream of the junction in both the main duct and the divergent duct, respectively. When the waste gases are not rich enough in CO content for efficient recovery, as in the initial and final stages of blowing, these dampers 9 are manipulated in such a manner to guide the waste gases to flow into the divergent duct. The deflected gases are then discharged into the atmosphere through the stack 8, after having being burned at the top portion thereof for complete combustion.
A recovery apparatus requires to be constructed to complete airtight structure, mainly for the following two reasons. First, since the waste gases from a converter have a more or less high content of CO, escape exposes the operator in the vicinity of the apparatus to the possible danger of intoxication. Secondly, admission of atmospheric air into the system can result in a reduction in quality of the recovered waste gas. In normal practice, to provide proper seal, a skirt 2 is mounted to enclose about the waste gas outlet where the converter 1 is connected to the gas cooler 3 of the recovery system, at which leak and entrance of atmospheric air are most likely to occur.
Since the mouth of oxygen blowing converters are rugged in the surface, the skirt 2 cannot be mounted to enclose the periphery of the converter mouth close enough to provide a physically airtight seal.
Consequently, most of those conventional skirts 2 are installed at a point some way off from the periphery of the converter leaving a largely annular air gap along the lower portion of the skirt 2. The waste gases through the mouth are drawn into the duct of the recovery apparatus by suction developed by the fan 6 which may, in operation, be adjusted to maintain a predetermined internal pressure in the gas cooler. As a consequence, admission of some amount of atmospheric air into the gas cooler through this gap is unavoidable, with a resultant reduction in CO gas content.
With the recent ever-increasing trends toward using the CO gas contained in the converter waste gases for useful applications such as the production of chemical substances, various techniques have been being developed to provide a complete airtight seal between the skirt and converter waste gas outlet for efficient CO gas recovery.
One such a development in the prior art, which might give some interesting comparison to the present invention, is illustrated in FIG. 4. Referring to the drawing, the skirt 2 is mounted about the gas cooler 3 of the recover apparatus just above the mouth of the converter 1. An annular sealing member 14 is provided below the skirt 2. The sealing member 14 is movably hinged on a horizontal pin in such a manner that, when the skirt 2 is placed into position, the sealing member 14 is brought into abutting contact with the flanged rim of the converter mouth 15. In the drawing, the numeral 11 indicates a tank of water for water sealing with a sealing plate 12 while the numeral 13 designating a hydraulic cylinder for travelling the skirt 2 in the vertical direction.
However, the flanged rim of the converter mouth tends to be covered in the surface with adhered lumps of slag and metal, the sealing member 14, when brought down into place by the descending skirt, is seated on a plane defined by the summits of such lumps leaving clevices along the bottom periphery of the member 14.